/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package studio.raptor.ddal.core.connection.jdbc.util;

import java.util.concurrent.Semaphore;

/**
 * This class implements a lock that can be used to suspend and resume the pool.  It
 * also provides a faux implementation that is used when the feature is disabled that
 * hopefully gets fully "optimized away" by the JIT.
 *
 * @author Brett Wooldridge
 */
public class SuspendResumeLock {

  public static final SuspendResumeLock FAUX_LOCK = new SuspendResumeLock(false) {
    @Override
    public void acquire() {
    }

    @Override
    public void release() {
    }

    @Override
    public void suspend() {
    }

    @Override
    public void resume() {
    }
  };

  private static final int MAX_PERMITS = 10000;
  private final Semaphore acquisitionSemaphore;

  /**
   * Default constructor
   */
  public SuspendResumeLock() {
    this(true);
  }

  private SuspendResumeLock(final boolean createSemaphore) {
    acquisitionSemaphore = (createSemaphore ? new Semaphore(MAX_PERMITS, true) : null);
  }

  public void acquire() {
    acquisitionSemaphore.acquireUninterruptibly();
  }

  public void release() {
    acquisitionSemaphore.release();
  }

  public void suspend() {
    acquisitionSemaphore.acquireUninterruptibly(MAX_PERMITS);
  }

  public void resume() {
    acquisitionSemaphore.release(MAX_PERMITS);
  }
}
